Polyamideimides (PAI) are amorphous high temperature engineering thermoplastics, which have excellent mechanical, electrical and thermal properties. These engineering resins can be used at temperatures well beyond the limits of most other high performance plastics and are stiffer and stronger at high temperatures of up to about 260.degree. C. than many high performance materials are at room temperature. Polyamideimides are reliable for long-term use at high temperatures, maintaining their dimensions under loads and at high temperatures. The low coefficients of linear thermal expansion allow the integration of polyamideimide components with metals. Polyamideimides can absorb impact energy better than most other high modulus materials. Polyamideimides are ideal for moving parts because they have low wear, excellent creep resistances and self-lubricity.
However, polyamideimides are often not used because their high melt viscosity causes significant pressure loss in conventional injection molding equipment. Polyamideimide can only be processed with equipment that has been modified to reduce the pressure loss. The expense and inconvenience of modifying equipment has made polyamideimide a less desirable material for product manufacturers.
Common processing aids, such as metal stearate, stearic acid, low molecular weight polyethylene and wax, are thermally degraded at the processing temperature of polyamideimide, which is typically at a temperature of about 350.degree. C. Often, polytetrafluoroethylene (PTFE) is used as a processing aid to improve the flow behavior of polyamideimide during injection molding. However, PTFE itself has a high viscosity, and it can cause plating lamination and some agglomeration even when a small amount, less than three percent by weight, of polytetrafluoroethylene is used. If more than 3% polytetrafluoroethylene is used, some of the mechanical properties of polyamideimides start to deteriorate. Using polytetrafluoroethylene as a processing aid has not been found to overcome the problems caused by the high viscosity of polyamideimide.
Therefore, a need exists for a polyamideimide thermoplastic composition that is easy to process, thermally and dimensionally stable at a high temperature, very solvent resistant, light weight with high mechanical properties and results in a lower final product cost with enhanced properties.